Method of cutting steel having a high chromium content



Patented Jan. 22, 1952 METHOD OF CUTTING STEEL HAVING A HIGH CHROMIUM CONTENT Cornelius J. Sullivan, Somerville, and Harold R.

Fisher, Metuchen, N. J., assignors to Air Reduction Company, Incorporated, a corporation of New York No Drawing. Application June 10, 1948,

Serial No. 32,276

2 Claims. 1

This invention relates to the oxygen cutting of alloy steels having a high chromium content.

Stainless steel, and other alloy steels containing a large percentage of chromium, are difficult to cut thermochemically with an oxygen cutting-torch because the chromium in the steel forms an oxide of such high melting point that it does not melt and flow away as molten slag but remains in the kerf and interferes with the cutting operation.

The principal object of this invention is to provide a thermochemical cutting method which makes possible the cutting of such alloy steels in an eflicient and economical way.

We have found that an alloy steel containing an amount of chromium which would ordinarily make thermochemical cutting of the alloy steel diilicult or impossible can be satisfactorily cut by using in the cutting-oxygen stream a flux comprising a material in powdered form which is adapted .to decompose at the temperature of the cutting reaction and release nascent oxygen. Among the substances that are adapted to do this and that are suitable for use in our method are barium peroxide, sodium peroxide, sodium chlorate, sodium perchlorate, potassium peroxide, and potassium permanganate.

According to the invention a flux comprising one or more of the above-mentioned or similar substances in powdered form adapted to release nascent oxygen at the temperature of the cutting reaction, is introduced into the cuttingoxygen stream at any convenient place so long as it will be present with the cutting-oxygen at the zone where the thermochemical action is taking place. It might even be projected as a separate stream into the kerf so that it is introduced into thecutting-oxygen stream at the zone where the thermochemical action is occurring, but preferably it is introduced into the cuttingoxygen stream before the cutting-oxygen reaches the cutting-torch.

Any suitable apparatus may be used for introducing the powdered flux uniformly and at the desired rate into the cutting-oxygen stream such as that described in the application of Joseph M. Tyrner, Serial No. 696,258, filed September 11, 1946, for Apparatus for Feeding Powdered Material, assigned to the assignee of the present application, and now Patent No. 2,549,033, issued April 17, 1951. The apparatus disclosed in the Tyrner application comprises an electrically vibrated feed hopper for the powdered material to be introduced into the oxygen stream, a gastight casing in which the feed hopper is located and having inlet and outlet connections by which the casing can be inserted in the cutting-oxygen line leading to the cutting-torch, the outlet being located in the bottom of the casing, and an electrically vibrated chute within the casing for receiving the powdered material vibrated out of the hopper and for conducting it to a position just over the oxygen outlet of the casing where it is sifted into the cutting-oxygen as it leaves the casing through the outlet.

The cutting-oxygen stream containing the powdered flux is projected by the cutting-torch against the high chromium content alloy steel while the metal is at kindling temperature and the cutting is effected thermochemically as is well understood in the art. The heating of the metal to its kindling temperature may be effected by the usual preheating flames of the cuttingtorch or in any other suitable way.

The exact manner in which the kind of flux material contemplated by the invention acts to facilitate the cutting of stainless steel and other alloy steels having a high chromium content is not known, but it is believed that the nascent oxygen released when the material breaks down at the high temperature of the cutting operation further oxidizes the refractory slag products to oxides of higher valance and in so doing produces a slag product of lower melting point. The slag consequently does not solidify but is maintained in fluid condition by the heat of the reaction and by the heat supplied by the usual preheating flames of the cutting-torch and therefore flows more readily out of the kerf and does not interfere with the cutting operation.

It is believed that any powdered material which will release nascent oxygen at the tem-, perature produced during the cutting operation will facilitate the oxygen cutting of stainless steel and other alloy steels having a large chromium content and is therefore suitable for use in our method, and the tests that have been made thus far bear this out. The tests, however, showed that of the materials tesed barium peroxide was the most suitable and produced the most satisfactory results.

We claim:

1. The method of thermochemically cutting alloy steel containing a percentage of'chromium; which renders the alloy steel difiicult to cut thermochemically, which comprises projecting a stream of cutting-oxygen against the alloy steel to be out while the metal is at kindling temperature, and introducing into the cutting-oxygen stream a flux in powdered form consisting essentially of barium peroxide.

3 2. The method of thermochemically cutting alloy steel containing a percentage of chromium which renders the alloy steel diificult to cut thermochemically, which comprises projecting a stream of cutting-oxygen against the alloy steel to be cut while the metal is at kindling temperature, and introducing into the cutting-oxygen stream a flux in powdered form consisting essentially of at least one material from the group consisting of barium peroxide, sodium peroxide, sodium chlorate, sodium perchlorate, potassium peroxide, and potassium permanganate.

CORNELIUS J. SULLIVAN. HAROLD R. FISHER.

REFERENCES CITED The following references are of record in the file of this patent:

4 UNITED STATES PATENTS Number Name Date 2,451,422 Wagner Oct. 12, 1948 2,454,325 Linnert Nov. 23, 1948 OTHER REFERENCES Smith's College Chemistry; 6th edition by Ehret, copyright 1946; published by D. Appleton- Century Co., New York, N. Y., page 382.

Sodovskii, treatise in Zavodskaya Lab. 8 No. 10-11, 1184 (1939); Khim. Referat. Zhim., 1940, No. 4, 57-8; as briefed in Chemical Abstracts, vol. 36, 1942, col. 3020.

Hedvall et a1., treatise in Arkiv. Kemi, Mineral. Geol. A19, No. 15, 9 pp., 1944; as briefed in Chemical Abstracts, Vol. 41, cols. 4055, 4056. 

2. THE METHOD OF THERMOCHEMICALLY CUTTING ALLOY STEEL CONTAINING A PERCENTAGE OF CHROMIUM WHICH RENDERS THE ALLOY STEEL DIFFICULT TO CUT THERMOCHEMICALLY, WHICH COMPRISES PROJECTING A STREAM OF CUTTING-OXYGEN AGAINST THE ALLOY STEEL TO BE CUT WHILE THE METAL IS AT KINDLING TEMPERATURE, AND INTRODUCING INTO THE CUTTING-OXYGEN STREAM A FLUX IN POWDERED FORM CONSISTING ESSENTIALLY OF AT LEAST ONE MATERIAL FROM THE GROUP CONSISTING OF BARIUM PEROXIDE, SODIUM PEROXIDE, SODIUM CHLORATE, SODIUM PERCHLORATE, POTASSIUM PEROXIDE, AND POTASSIUM PERMANGANATE. 